Low-temperature burner



Mamh 31 1931. c CARTER 1,798,785

LOW TEMPERATURE BURNER Filed March 24, 1930 FIGI Patented Mar. 31, 1931UNITED STATES PATENT OFFICE now-rnnrnnarunn BURNER Application filedMarch 24, 1930. Serial No. 438,587.

contents to the desired temperature of treatment by means of a largeflame and, this tem- 1 perature once attained, to maintain it by meansof a relatively small flame supplying only such heat as is lost byradiation. It is also desirable in a furnace used to heat metal attemperatures ranging from 1,300 F. to 2,000 F. for the purpose ofquenching or hardening and to reheat such metal, for the purpose ofdrawing or tempering, to a tem- I perature somewhere between roomtemperature and 1,250 F. and to maintain such temperature evenly for asustained period.

For this purpose the gas burners heretofore used are unsuitable as, whenthey are made of sufficient size to heat the furnace at the desiredspeed or to the desired temperature, they are unreliable when turneddown to such a degree as to maintain furnace temperature constant, theflame tending to blow off the tip of the burner. It is therefore commonpractice to use two burners, a large size for heating up and a smallsize for main taining temperature, or to use a single large burnerintermittently.

By the use of my improved device it is easy to maintain a temperature of200 to 2,000

F. indefinitely, with a single burner, while with the burners now in usefor temperatures say from 1,400 to 1,800 F. it is difficult to maintaina temperature below 1,000 F. without encountering serious trouble inadjustment and in keeping the flame alight.

Attention is directed to the attached drawing, Fig. 1, showing anillustrative embodiment of my invention in longitudinal section, and tothe following description thereof. Referring to Fig. 1, 10 is a gasburner of any known or preferred type, supplied with the usual mixtureof air and gas by means of pipes and valves not shown, and producing aflame as at 11.

A. tubular inner easing l2 surrounding the till burner is provided witha closed end 13 bored to fit over the burner proper and held thereon bya set screw or similar means 14;, so that the burner may be withdrawnfrom and adjusted in position within the surrounding 5 elements. Thiscasing has a relatively slight clearance 15, sayan inch or a fractionthereof, around the burner, and is arranged to project for a shortdistance beyond the burner tip as indicated at 16. This projection ismuch'tobe preferred as it enables the inner casing to withdraw heat fromthe flame for a purpose which will a pear, and as it prevents the flamefrom' ing blown off the burner tip by following air currents set up bythe flame. I

The innercasing is surrounded by an outer casing 17 which-is preferablypermanently attached to the inner casing as by the weld in dicated at18. A narrow annular channel 22 is left between the two casings. The

manner of making this joint is immaterial so long as it is rigid andsubstantially free from air leakage. The open end of the outer casingpreferably projects beyond the end of theinner casing as indicated at19. This end of the outer casing is sealed into the furnace wall in suchmanner as to project the flame into the furnace. A pipe 20 controlled bya valve 21 communicates with the closed end of the casing for thepurpose of admitting a controlled supply of air, though this air may beadmitted through holes in the casing or in any other preferred manner.

Gas burners are not novel and casings similar to the outer casing 17have heretofore been used as a means of introducing the burner into thefurnace wall. I do not claim either of these elements as such, the meritof my invention residing in so shielding the burner within the outercasing (as by means of the inner casing 12) that secondary or coolingair encounters the flame only at a right or an obtuse angle, thuspreventing the formation of the air currents parallel to the flamewhich, in prior forms, have tended to draw the flame from the burner tipand thus extinguish it. a

This inner casing serves several objects. First, it shields theleurnertip from gas carrents arising in the furnace and from aircurrents due to the introduction of secondary air into the outer casing.Second, and most important, it permits the burner proper to be soadjusted as to carry a very small flame, this fiame meeting thesecondary air entering through pipe 20 in the space indicated at 16 inthe drawing. The jet of mixture issuing from the tip of the burner isthus reduced in velocity by eddying and counterflow in the space 16 andthe liability to blow ofi the tip is correspondingly reduced.

Third, the two casings withdraw a material amount of heat from the flameand transfer this heat to the air passing through the annular channel22, thus materially tending to equalize temperatures in the combustionzone and aiding greatly in keeping a small flame alive.

Fourth, the relatively cool air when mixed with the heated products ofcombustion permits the temperature to be adjusted to any point lowerthan that of the filame in proportion to the amount of air admitted.

I claim as my invention:

1. Apparatus for maintaining a flame of low volume and intensity,comprising: a tubular gas burner having a tip pointed in the directionof the gas flow; an unobstructed inner casing surrounding said burnerleaving an annular space therebetween, said casing being open at the endadjacent the tip of said burner and projecting beyond said tip; aclosure for the opposite end of said inner casing, said closure slidablyengaging the exterior of said burner; means for adjusting the extent ofsaid projection; an outer casing substantially concentric with andspaced from said inner casing, said outer casing being open at the endadjacent said burner tip and nonleakably and integrally attached to saidinner casing at the opposite end, and means for controllably introducingan air supply into the space between said casings.

2. Apparatus for maintaining a flame of low volume and intensity,comprising: an inner casing surrounding a gas burner, the end of saidcasing adjacent the tip of said burner being open and the opposite endof said casing being closed; an outer casing open at one end and sealedover said inner casing adjacent the closed end thereof so as to make therelation between the inner and outer casings a fixed one and means forcontrollably introducing an air supply into the space be tween saidcasings, and means for varying the longitudinal position of the gasburner within the inner and outer casings.

3. Apparatus for maintaining a flame of low volume and intensity,comprising: an inner asin surrounding and spaced from a gas burneraavinga forward pointing conical tip and projecting beyond the tip of saidburner, the end of said casing adjacent said tip being open and theopposite end of said

